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Ultrasonic wave and moduli changes in a curing epoxy resin

Ultrasonic techniques are examined as a means for monitoring reaction extent and the development of solid-phase moduli in a curing epoxy

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Abstract

During the cure cycle, thermosetting polymeric resins change in physical character from a viscous liquid to a gel and finally to a hardened solid. Ultrasonic-wave-propagation techniques can be used to monitor both the extent of cure and the development of solid-phase moduli. This paper outlines such a program and presents results for a room-temperature, amine-cured epoxy system. Signal attenuation and wave-speed data are given as a function of cure time for 1.0 MHz longitudinal and shear waves. The behavior observed is first interpreted in terms of linear-viscoelastic wave-propagation theory. Then using the wave speeds, apparent elastic moduli are calculated as a function of cure time. Finally, relations are developed which suggest a mapping between the moduli and a normalized reaction-extent variable. Implicit in these relations is that the moduli themselves can serve or be viewed as reaction-extent variables.

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Abbreviations

C L :

longitudinal-wave speed (mm/μs)

C s :

shear-wave speed (mm/μs)

E :

Young's modulus (GPa)

F :

longitudinal modulus (GPa)

G, G 0 , G ∞ :

shear moduli (GPa)

h :

thickness (mm)

K :

bulk modulus (GPa)

k :

reaction constant (h−1)

T g :

glass transition temperature (°C)

t :

time coordinate (h, s)

V 1 :

first-echo amplitude (V)

V 2 :

second-echo amplitude (V)

V REF :

reference-echo amplitude (V)

α:

absolute attenuation (Np/mm)

αR :

relative attenuation index

αREF :

reference absolute attenuation (Np/mm)

β:

relaxation time reciprocal (s−1)

γ:

reaction constant (h−1)

ν:

Poisson's ratio

ξ:

reaction-extent variable

ϱ:

mass density (gm/cm3)

τ:

relaxation time(s)

ω:

circular frequncy (rad/s)

References

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Authors and Affiliations

  1. Storage Technical Corporation, 80027, Louisville, CO

    Albert M. Lindrose

Authors
  1. Albert M. Lindrose
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Additional information

Albert M. Lindrose was Member, Technical Staff, Sandia Laboratories, Albuquerque, NM 87115

This work was supported by the U.S. Energy Research and Development Administration.

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Lindrose, A.M. Ultrasonic wave and moduli changes in a curing epoxy resin. Experimental Mechanics 18, 227–232 (1978). https://doi.org/10.1007/BF02328418

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  • DOI: https://doi.org/10.1007/BF02328418

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